Generally employed in a vehicle such as a rear two-axle heavy-duty truck is a so-called trunnion suspension which is a suspension intended for exclusive use with axles in tandem.
FIGS. 1-5 show an example of a conventional trunnion suspension structure in which a pair of axles 1 and 2 are arranged in tandem with a required space longitudinally of a vehicle, a trunnion shaft 3 being arranged therebetween and fixed through trunnion brackets 4 to a frame 5. Pivotally mounted on the trunnion shaft 3 are central portions of leaf springs 6 through pivotal bases 7. The front and back axles 1 and 2 are respectively supported by opposite ends of the leaf springs 6 and are kept in position longitudinally of the vehicle by upper and lower rods 8 and 9.
A cross member 10 laterally bridges over the frame 5 for reinforcement at the fixed positions of the trunnion brackets 4 to the frame 5. The upper rods 8 connect front and rear surfaces on a central portion of the cross member 10 with upper surfaces on central portions of the axles 1 and 2, respectively; the lower rods 9 connect front and rear surface on lower portions of the trunnion brackets 4 with lower portions of opposite ends of the axles 1 and 2, respectively.
In the trunnion suspension structure, vertical movements of the front and back axle 1 and 2 are absorbed by the leaf springs 6, and longitudinal forces are transmitted through the upper and lower rods 8 and 9 to the frame 5. When the rear wheels of the vehicle are to step over a difference in level, satisfactory stepping-over is realized by pivotal movements of the leaf springs 6 about the trunnion shaft 3.
In the figures, reference numeral 11 denotes U bolts for fixing the central portion of the leaf spring 6 to the pivotal base 7; 12, mounting parts on the front and rear surfaces on the central portion of the cross member 10, respectively, for mounting of the upper rods 8; 13, mounting parts on the upper surfaces on the axles 1 and 2, respectively, for mounting of the upper rods 8; 14, mounting parts on the front and rear surfaces of the lower portions of the trunnion brackets 4, respectively, for mounting of the lower rods 9; and 15, mounting parts on the lower portions of the opposite ends of the axles 1 and 2, respectively, for mounting of the lower rods 9.
There exists, for example, the following Patent Literature 1 as conventional art document pertinent to a trunnion suspension structure as mentioned in the above.